Katsumi Yoshizawa

Full-mesh T- and O-band wavelength router based on arrayed waveguide gratings.

We propose an ultra-broadband full-mesh wavelength router supporting the T- and O-bands using 3 stages of cascaded arrayed waveguide gratings (AWGs). The router architecture is based on a combination of waveband and channel routing by coarse and fine AWGs, respectively. We fabricated several T-band-specific silica-based AWGs and quantum dot semiconductor optical ampliers as part of the router, and demonstrated 10 Gbps data transmission for several wavelengths throughout a range of 7.4 THz. The power penalties were below 1 dB. Wavelength routing was also demonstrated, where tuning time within a 9.4-nm-wide waveband was below 400 ms.

A WDM/TDM Access Network Based on Broad T-Band Wavelength Resource Using Quantum Dot Semiconductor Devices

A wavelength-division multiplexing/time-division multiplexing (WDM/TDM) network exploiting the broad wavelength range of T-band (1000-1260 nm) is proposed. The network is based on different wavebands of downlink and uplink channels, with each transmitter consisting of a wavelength tunable laser utilized for more than one user through wavelength tuning. The downlink section of the network also introduces interconnecting optical lines and semiconductor optical amplifiers (SOAs), pairing up each of the downlink wavebands to provide structural redundancy by allowing transmitters to be shared between the paired wavebands through TDM. Quantum dot (QD)-based wavelength tunable lasers and SOAs were fabricated for a preliminary demonstration experiment. Error-free transmission with less than 1 dB of power penalty was obtained for a wavelength range of 24.2 nm (5.6 THz). The QD-SOAs exhibited a decent rise and fall time, as well as extinction ratios throughout the wavelength range, which enable it to be used as path switches.

Demonstration of 10-Gbit/s transmission over G.652 fiber for T-band optical access systems using quantum-dot semiconductor devices

The wavelength range of 1000–1260 nm, known as T-band, where T denotes “thousand”, is one of the promising wavebands suitable for the future moderate-range optical networks. We have developed T-band specific semiconductor devices based on quantum-dot technology. However, the cut-off wavelength of optical fiber cables currently utilized in access networks, i.e., G.652 fibers, is specified to be less than 1260 nm. Therefore, the fibers do not fully support the T-band. This letter presents a demonstration of the feasibility of 10-Gbit/s transmission over G.652 fibers in the T-band by experiments.

Feasibility study of adaptive gain control of quantum-dot SOA for unicast/multicast wavelength selective routing systems in T-band

Optical multicast routing is used for many applications such as video streaming and energy-efficient networking. We propose adaptive gain control of a quantum-dot-based semiconductor optical amplifier (QD-SOA) for optical unicast and multicast wavelength selective routing systems in T-band to compensate optical power loss according to the number of destination nodes.

Wavelength-selective external cavity laser using an InAs quantum dot gain chip and a planar lightwave circuit for T-band WDM communications

Short-reach, low-cost, and large-capacity optical transport systems can be realized by using the T-band (1000–1260 nm) because it has five times wider bandwidth than that of the C- and L-bands combined [1]. In this study, we developed a wavelength-selective external cavity laser using an InAs quantum dot (QD) gain chip and a planar lightwave circuit (PLC) for T-band communications [2]. Fig. 1 shows the configuration of the proposed external cavity laser. It consists of an InAs QD gain chip, two aspheric lenses, and a PLC. The 1 × 16 optical switch, the arrayed-waveguide grating (AWG), and the directional coupler are integrated on a silica PLC chip. The facets of the gain chip and the PLC chip with high-reflection coatings, as shown in Fig. 1, configure the laser cavity. The light emitted from the gain chip is focused onto the PLC chip through the lenses and then enters one of the input waveguides of the AWG. The 1×16 switch is composed of 15 1×2 Mach-Zehnder interferometer switches, and the lasing wavelength can be selected by switching the input waveguide of the AWG. In the QD gain chip, multi-stacked InAs QD layers are sandwiched between AlGaAs cladding layers grown on a GaAs substrate [3]. The 3-dB amplified spontaneous emission spectrum ranges from 1033 nm to 1067 nm at an injection current of 200 mA. The AWG is designed with a center wavelength of 1060 nm, FSR of 10.3 THz, and charmel spacing of 400 GHz, and it has 16 input waveguides.

Experimental Demonstration of 4K-UHD Video Transmission Using T-Band Wavelength Routing System for Passive Optical Local Area Networks

We demonstrate uncompressed 4K-UHD video transmission in the optical communication wavelength range known as T-band. The experiments using quantum-dot semiconductor devices and an arrayed waveguide grating router show the feasibility of T-band passive optical local area networks.

Wavelength-Selective External-Cavity Laser Using an Optical Switch Integrated Arrayed-Waveguide Grating for T-band Communications

An external-cavity laser using a 1×16 optical switch integrated arrayed-waveguide grating is configured. Error-free transmissions of 12.5-Gbps signal for 16 channels within the wavelength range of 1049.7-1071.9 nm, and a switching time of less than 10 ms are confirmed.

Polarization diversity quantum dot semiconductor optical amplifier module for T-band communication

The polarization independent SOA module for T-band communication was fabricated using the quantum dot gain chip and the polarization diversity circuits with photonic crystal waveplates. The polarization dependent gain was successfully reduced to 0.5 dB.

External cavity laser using a InAs quantum dot gain chip and an arrayed-waveguide grating for T-band optical communications

Utilizing T-band (1000 nm to 1260 nm) for optical communications is promising for short reach, and large capacity networks, such as data centers or access networks. It is feasible to use this with low-cost coarse wavelength division multiplexing (WDM). However, a tunable wavelength light source is necessary for such applications. In this paper, we propose a new configuration for an external cavity laser, which uses a silica-based arrayed waveguide grating (AWG) for the wavelength selecting element. The external cavity laser consists of a gain chip with high reflection (HR) and anti-reflection (AR) coated facets, coupling lenses, an AWG with AR/HR coatings, and an output fiber. The AWG has 17 connection ports, which correspond to 17 wavelengths with a channel spacing of 1.67 nm. The width of the connection port waveguides was optimized to achieve high coupling efficiency. The AWG chip size is 15 mm x 30 mm. The active layer in the gain chip has InAs quantum dots. The spontaneous emission 3-dB bandwidth was 48 nm (1108 nm to 1156 nm) when a current of 150 mA was injected into the gain chip. The lasing wavelength of the external cavity laser was successfully tuned from 1129.9 nm to 1154.4 nm by selecting the connection ports of the AWG. The typical threshold current was about 130 mA.